Luteinizing hormone (lutropin or LH), along with follicle-stimulating hormone (FSH) are the pituitary gonadotropins which regulate gonadal-steroid biosynthesis and gametogenesis. LH is a glycoprotein hormone that is synthesized and secreted by the gonadotropes of the anterior pituitary gland of most mammals and lower vertebrates and is essential for normal growth and sexual development and reproduction. It is a member of a family of structurally-related polypeptide hormones that also includes pituitary FSH and thyrotropin, and placental chorionic gonadotropin and is composed of two different subunits called Alpha and Beta which are associated non-covalently. Our laboratory has recently isolated and characterized cDNAs and natural genes encoding the Alpha and Beta subunits of rat LH. These DNAs serve as molecular hybridization probes which have allowed us to develop a sensitive blot hybridization assay to determine the steady-state levels of the specific mRNAs which encode the subunits of LH in the pituitary gonadotrope in vivo and in vitro. Hence, we propose to evaluate the effects of various physiologic states and known regulators or LH secretion and synthesis on the expression of the genes that represent the subunits of rat LH. In particular, we will study the effect of special endocrinologic states on the synthesis of LH as manifested in the changes in levels of steady-state subunit mRNAs. These states include the development of gonadotropic function in the young animal, sexual maturation, the strus cycle, and castration. We also wish to study the effects of gonadotropin-releasing-hormone and the gonadal steroids on LH subunit synthesis in the intact normal and gonadectomized animal as well as in cultured rat pituicytes and pituitary glands in organ culture. A major goal in our work is an understanding at the molecular level of the positive and negative feedback effects of the gonadal steroids including estrogen, progesterone, and testosterone on LH subunit synthesis and LH subunit gene expression. Progress in these areas will improve our knowledge of the functioning of the hypothalamic-pituitary-gonadal axis and its role in reproductive medicine. In summary, we wish to evaluate the regulation of the synthesis of the subunits of LH at the pre-translational level as modulated by specific hormones and physiologic states.